Asian Spine J.  2020 Dec;14(6):773-781. 10.31616/asj.2020.0041.

Morphological Changes in the Ligamentum Flavum in Degenerative Lumbar Canal Stenosis: A Prospective, Comparative Study

Affiliations
  • 1Department of Orthopaedics, All India Institute of Medical Sciences, New Delhi, India
  • 2Department of Pathology, All India Institute of Medical Sciences, New Delhi, India
  • 3Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India
  • 4Department of Orthopaedics, Jai Prakash Narayan Apex Trauma Centre, New Delhi, India

Abstract

Study Design: Prospective, comparative. Purpose: To compare the histopathological and electron microscopic changes in the ligamentum flavum (LF) between degenerative lumbar canal stenosis (LCS) and lumbar disk herniation (LDH). Overview of Literature: The LF has been implicated as a key structure in the pathogenesis of LCS. With aging, the LF undergoes morphological changes–a decrease in the elastic component and an increase in the collagen component, in addition to other focal changes. By comparing the histopathological and electron microscopic picture of the LF in elderly patients with LCS with that in young patients with LDH, the role of this ligament in the pathogenesis of LCS may be clarified.
Methods
Forty patients were prospectively recruited and divided into two groups: group 1 included 20 patients with degenerative LCS aged >55 years and group 2 included patients with LDH aged <35 years. The ligament flava were collected during the patients’ surgery. The features noted on histopathological examination included the fibrosis score, the loss of elastic fibers, calcification, chondroid metaplasia, mucinous degeneration, vascularization, long septa, clefts, granulation tissue, and ganglion-like cysts. The features noted on electron microscopic examination included the elastic fiber thickness, the quality of elastic fibers, the elastic:collagen ratio, calcification, melanin fibers, remnants of necrotic cells, and electron-dense material in the LF. All parameters were compared between group 1 and group 2.
Results
On histopathological examination, the two groups exhibited significant differences regarding three parameters: chondroid metaplasia, long septa, and ganglion-like cysts. On electron microscopy examination, significant differences were observed between the two groups regarding two parameters: the quality of elastic fibers and the elastic:collagen ratio.
Conclusions
Characteristic morphological changes may be noted on histopathological and electron microscopic examination that mark the degenerative changes in the LF that contribute to the occurrence and pathogenesis of degenerative LCS.

Keyword

Degenerative intervertebral disks; Electron microscopy; Histopathology; Ligamentum flavum; Lumbar region
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